A Biological Organism
by willowscribe
Summary: Tony Stark is a biological organism. When biological organisms run out of food, water, and oxygen, they die. Tony Stark is a biological organism, and he's not going to let that happen to him. (AKA: my gut reaction to the Avengers: Endgame trailer)


**Can we just talk about that Avengers: Endgame trailer? Because that nonsense messed me up. I was not ready for it to start with Tony's farewell speech, and there is no way that I can wait until April to see how it ends. I needed a solution for Tony NOW.**

 **Thus, this quick fic. As always, any reviews you may offer are loved and cherished.**

 **This work is cross-posted on AO3.**

 _A Biological Organism_

The ship is cold.

That's the worst part, Tony thinks. Not the hopelessness, not the gnawing hunger, not the thirst that cannot be sated even with his own urine. It's the cold.

It's bone-deep. The ship was never meant for an organism like Tony. The frigid air tears through his lungs and would make his eyes water if he weren't so dehydrated that even simple biological functions like lubricated eyeballs seem like luxuries.

Nebula isn't the worst company in the world, but she's certainly not the best either. She keeps to herself, says very little, and generally tries to fade into the background. Considering there's only two of them on the ship, and only one of them requires organic functions (food, water, and sleep, for example), Nebula has an easy time avoiding Tony.

She's mourning, Tony knows. She lost her sister to Thanos, just like Tony lost his son.

He can admit that now, weeks after the fact. Maybe it's the clarity that impending suffocation brings, but Tony would proudly tell anyone and everyone that he considers Peter Parker the closest thing he has to a son.

Considered, anyway. Past tense.

After a while, the shivers from the cold give way to sweating and feverish delirium. Rationally, Tony knows it's hypothermia and that he shouldn't listen to the mixed-up cues his brain is giving him, but irrationally, Tony pulls his ruined shirt off anyway, leaving only a black tank-top in an effort to thwart the hot flash that overwhelms him. He records a farewell message to Pepper – and God, he doesn't even know if she's still alive to be able to hear it.

The oxygen is due to run out in ten hours, and even a genius like Tony requires oxygen to survive. It's a function of his humanity. It's a _weakness_ of his humanity.

Tony likes his humanity. He's rather fond of it, especially after he had the surgery to remove the arc reactor. He likes knowing that he is made of flesh and blood, that he is real and alive and _present_. The idea of relying on a foreign object to survive a great trauma would be devastating to have to do for a second time.

And yet…

Tony Stark has never been one to lie down and accept the hand Fate has dealt him.

[-]

At least a high-tech spaceship like this one has a lab, Tony reflects. It's not necessarily appointed like a lab one would find on what Nebula calls "Terra," but any kind of scientific equipment suits Tony's purposes at the moment. The nanotech stored in the arc reactor can't reconstruct the suit without the appropriate blueprint being uploaded into the nanotubes, but the nanotubes themselves are still functional, ready to be loaded up with any blueprint Tony can think of. They are an elegant delivery system for an inelegant solution.

Tony remembers the genetic sequence for Extremis. How could he not, after coming up with the solution in order to save Pepper's life? He codes the biological blueprint on a computer-like machine that has seen better days, and when he uploads it into the arc reactor, it sparks and hisses ominously as it utilizes all of its RAM. Tony adds a few tricks of his own into the sequencing – he removes the increased strength and stamina and instead programs in a digital interface for the human brain. He doesn't need superpowers. What he needs is a backup system.

When the virus is ready, Tony finds Nebula and asks her to help him administer it. She's not thrilled about the idea of cutting open Tony's chest to remove the artificial sternum and replace the arc reactor inside his thoracic cavity, but she agrees for reasons Tony does not understand but is grateful for regardless. After the arc reactor is plugged into his heart, the nanotubes will be pumped throughout his circulatory system and will make their way to Tony's brain.

It's a long shot, but Tony figures he'll be dead by morning if he does nothing. A one percent success rate is still a better bet than a zero percent one.

[-]

In a spaceship drifting aimlessly through the dark of the universe, Nebula tends to the brain-dead shell of a Terran. Its body is only barely kept alive by the virus that repairs all biological damage, but its brain is long-gone. Nonetheless, Nebula keeps watch.

[-]

At the Compound, Steve Rogers watches the security cameras listlessly. Ever since Scott's unexpected arrival, he'd been holding out the faint, desperate hope that there would be more to follow. Clint, maybe, or Nick and Maria.

When the camera feed goes fuzzy for a minute, Steve sits up from where he'd been slumped and leans forward to investigate. When the feed cuts back to the empty driveway, Steve sighs wearily and sits back again. It wasn't worth getting his hopes up. It never seems to be.

Then, there's the sound of a throat being cleared. Steve glances up, and when he does, he sees that the holo-screen they used to use for conference calls is lit up. On the screen, looking sheepish and vaguely two-dimensional, is Tony Stark.

"Hey Cap," he says softly, his eyes warm despite the cold blue pixels that make up his image.

"Tony," Steve breathes, his eyes barely able to comprehend what he's seeing. "What are you…? How are you alive? What's going on?"

Tony clucks his tongue against his teeth. "I'm kind of in two places at once," he says, sounding weary. "I may have had to upload myself into a Stark satellite server in order to preserve my brain function, which incidentally connects me with all wireless technology that the satellite can access. As for my body, well…" He shrugs. "It may still be alive. I'm not entirely sure. I was on a spaceship heading to Earth, but we weren't going to make it back in time." He grimaces. "This was the only option."

For a brief moment, Steve is reminded of the AI that Zola left at Camp Lehigh, but he shakes off that thought at once. This is _Tony_ , the man he's learned to trust after years of fighting together and even more years of therapy after what happened in Siberia. This is _Tony_ , Earth's best defender. This is _Tony_ , the man Steve once called a friend.

He trusts him.

"What do I need to do?"

[-]

For once, Steve Rogers reflects while Tony chatters through the speaker system, there's a glimmer of hope for the future.


End file.
